Abstract

Studies of the dissociation dynamics of cluster ions provide insight into the process of energy disposal for mass-selected species. Detailed investigations of the photodissociation of the cluster anions ${\left({\text{SO}}_2\right)}_2^{-}$ and ${\text{CO}}_3^{-}{\left({\text{H}}_2\text{O}\right)}_n(0\le n\le 3)$ have been accomplished for mass-selected ion species using an intracavity dye laser pumped with an argon-ion laser. in the case of ${\text{CO}}_3^{-}$, the unhydrated parent ion is observed to have a bound electronic excited state through which absorption of a second photon proceeds to a repulsive state leading to the ejection of O^-. There are two possible mechanisms for ${\text{CO}}_3^{\text{-}}$ hydrate dissociation: one is a repulsive and the second a predissociative mechanism. In both, cluster dissociation is initiated by the same ${}^2{A}_1{\leftarrow }^2{B}_1$ transition from the ground to a weakly bound excited state of the core ion and leads to the loss of all water molecules within the time of observation. In the photodissociation of ${\text{CO}}_3^{\text{-}}$, ${\text{CO}}_3^{\text{-}}{\left({\text{H}}_2\text{O}\right)}_{1,2,3}$, and ${\left({\text{SO}}_2\right)}_2^{\text{-}}$ considerable excess energy is partitioned into relative translation of the photoproducts. Through studies of energy release in ${\left({\text{SO}}_2\right)}_2^{\text{-}}$ with photons of parallel and perpendicular polarization, evidence has been obtained that the lifetime of the complex preceding photodissociation is less than a rotational period. The implications of the findings are discussed in terms of phase space theory.

© 1986 Optical Society of America